This invention relates to an improved dry bleach and stable enzyme granular compositions.
During the last score of years the use of enzymes, especially of microbial origin, has been more and more common. Enzymes are used in, for example, the starch industry to produce glucose and fructose by means of amylases, amylglucosidases and glucose isomerases. In the dairy industry a vast tonnage of rennets is used and in the detergent industry proteases are normally used as additives in the washing powders to impart a better action on proteinaceous stains on the laundry.
On July 7, 1970, C. B. McCarty was granted U.S. Pat. No. 3,519,570 for enzyme-containing detergent compositions and a process for conglutination of enzymes and detergents. U.S. Pat. No. 3,784,476, van Kampen et al., issued Jan. 8, 1974, discloses a particulate enzyme-containing detergent composition containing a detergent surface-active agent, a water-soluble builder salt and discrete, shaped inorganic solids containing proteolytic or amylolytic enzymes. It should be noted that this patent does not teach an enzyme granulate with alkaline buffer salt as defined herein (pH of 7-11) used in combination with a peroxyacid bleach as disclosed herein.
U.S. Pat. No. 4,106,991, Markensen et al., issued Aug. 15, 1978, incorporated herein in its entirety, discloses an improved formation for enzyme granulates comprising enzyme, inorganic salts, a granulation binder, and finely divided cellulose fibers as 2-40% by weight of the granulate. Optionally, a waxy substance can be employed for the granulating agent, or to coat the granulate.
The granulates so produced are reported by Markensen et al. to have a higher physical stability and a higher resistance against abrasion than granulates without cellulose fibers and, consequently, a very low dust level. Markensen et al. does not disclose that use of alkaline buffer salts would improve the enzyme stability in the presence of peroxyacid bleach.
After the development of the granulated and coated enzymes presently offered to the detergent industry, the use of the enzymes in detergents has grown steadily.
Making a storage stable mixture of enzyme containing granulates and dry peroxyacid bleach granulates is a difficult task. In spite of the fact that some commercially available enzyme granulates are advertised as "perborate bleach stable," they are weak storagewise in the presence of strong peroxyacid bleach granulates. It should be noted that peroxyacid bleach granulates are relatively newcomers to the dry commercial laundry detergent and bleach markets. The term "bleach" as used herein unless otherwise specified means peroxyacid bleach and the terms "peroxyacid bleach powder" and "peroxyacid bleach granulates" are synonymous unless otherwise specified. The term "enzyme" as used hereinafter means raw enzyme, unless otherwise specified. The term "enzyme powder" means a mixture os raw enzyme and inorganic salts.